1. Field of Industrial Usefulness
This invention relates to a power change-over mechanism of a vehicle for industrial machinery, which permits free change-over between four-wheel drive and two-wheel drive.
2. Prior Art
In FIG. 1 showing a conventional embodiment, a first driving shaft 1 for driving a rear wheel and a second driving shaft 2 for driving a front wheel are both aligned on the same axis center, and at the same time they have outward splines 3, 4 respectively. A high-speed gear 5 and a low-speed gear 6 fit onto the first and second driving shafts 1, 2 through bearings 7, 7a, and at the same time they have inward splines 8, 9 respectively. An annular power change-over spool (spline joint) 10 has an inward spline 11 and a pair of outward splines 13, 14 and at the same time it provides an annular groove 16 for engagement with a shift fork and spline fits onto the first driving shaft 1 freely slidingly operably in the axial direction.
In case of the four-wheel drive, the spool 10 is shifted forward to interconnect the low-speed gear 6 through the spool 10 to the first and second shafts, 1, 2. Namely, a power transmitted from an engine through a transmission to the low-speed gear 6 is transmitted through the splines 9, 14 to the spool 10, and further transmitted from the spool 10 to the first driving shaft 1 through means of the splines 11, 3 and to the second driving shaft 2 through means of the splines 11, 4.
In case of the two-wheel, the spool 10 is shifted rearward to interconnect the high-speed gear 5 through the spool 10 to the first driving shaft 1. Namely, the power transmitted from the engine through the transmission to the high-speed gear 5 is transmitted through the splines 8, 13 to the spool 10, and further transmitted from the spool 10 to the first driving shaft 1 through means of the splines 11, 3 to drive the rear wheel.
However, in case when the power change-over mechanism is composed of the power change-over annular spool 10 as a member, the following disadvantages will arise at the time of change-over. Generally, in case of power change-over, a power from an engine has previously been cut off by means of a clutch etc. and the change-over operation is done with a vehicle stopped. However, in case of change-over from the two-wheel drive to the four-wheel drive, meshing of gears is under fixed condition because of the driving shaft 1 being interconnected to the rear wheel and the driving shaft 2 being interconnected to the front wheel, so that the spline 11 of the spool 10 would not mesh with spline 4 of the driving shaft 2 to make the change-over from the two-wheel drive into the four-wheel drive impossible.
Further, under a normal four-wheel drive operation, a torsion will be produced between the driving shafts 1, 2 due to slippage of wheel and large contact forces will be generated between the spline 3 of the driving shaft 1 and the spline 11 of the spool 10 and between the spline 4 of the driving shaft 2 and the spline 12 of the spool 10, so that the spool 10 would not slide to make the change-over from the four-wheel drive into the two-wheel drive impossible. For this reason, a change-over from a high-speed into a low-speed or a change-over from a low-speed into a high-speed will naturally become impossible.
The applicant of this invention proposed in the application (Japan Ser. No. S58-108286; U.S. Ser. No. 621,318 now U.S. Pat. No. 4,553,623), as a means to improved the above disadvantage, the means in which the change-over spool was divided into two: the outer peripheral side member and the inner peripheral side member, and the both members were spline fitted axially slidingly each other through the damper. However, the phenomenon of change-over from the four-wheel drive to the two-wheel drive being impossible was not completely dissolved because a power was directly transmitted between the outer peripheral side member and the inner peripheral side member when they were spline connected.
3. Object of the Invention
An object of this invention is to enable the disadvantage of the conventional embodiment shown in FIG. 1 to be more perfectly dissolved by improving said mechanism of application No. S58-108286, i.e. to simple and securely enable the change-over between four-wheel drive and two-wheel drive and the change-over between high-speed and low-speed by operating one set of spool only once even under a condition where the driving shafts of front and rear wheels do not mesh each other due to deviation of spline phase thereof, or under a condition where a torsion is produced between the driving shafts of the front and rear wheels.
In order to accomplish the above object, in a power change-over mechanism of this invention, a spool is divided into two; an outer peripheral side member having splines freely meshed with splines of high-speed and low-speed gears and an inner peripheral side member having a spline freely meshed with splines of said driving shafts, an inner peripheral sub-spline constantly meshing with the first driving shaft is further formed on the outer peripheral member, the outer peripheral member is clearance fitted onto an outer periphery of the inner peripheral member, and the outer and inner peripheral members are relatively movably connected in the axial direction through a damper means.